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27 March 2009

Cougar S-92 timeline: TSB

The Transportation Safety Board released a time line for Cougar’s CHI91, the Sikorsky S-92 that crashed two weeks ago. Compare it to one published online at the time of the incident. The TSB timeline is given in ZULU while the flightaware.com tracklog is converted from ZULU to Eastern Daylight. Local time for the incident is ZULU – 3.5.

One of the questions the timeline raises is the search and rescue helicopter response time. Not the Cormorant’s from 103 Squadron in Gander, mind you but Cougar’s own SAR helo.

If we take CHI91’s MAYDAY as minute zero, the figures get interesting.

Cougar should have an operations base monitoring the flight and its radio communications. There would likely also be a channel available so that the pilots can speak directly to the company’s maintenance and senior pilot team.

With that said, Cougar Base at St. John’s airport should have been aware of the emergency no later than M+0, the same time that Gander received the MAYDAY.

The aircraft ditches at M+11.

At M+11 Cougar base advises that they will launch Cougar 61, the SAR helicopter. The company had been operating as back-up to 103 and knew at that time that the air force SAR response was an additional one hour flying time away.

Cougar 61 does not launch until M+43.

Cougar 61 arrives on scene 18 minutes later. An aircraft 18 minutes flying time away takes 43 minutes to get airborne and that’s in a situation where the aircraft ought to have been ready as a matter of normal procedure and the despatchers knew from the outset that there was a potentially catastrophic problem with the aircraft.

We can say they knew it was potentially catastrophic because they know the importance of the main gearbox oil pressure to continued flight. Heck, they would have known about the Broome incident that had led to the January Sikorsky directive.

This is one of many questions that the TSB investigation will undoubtedly address with typical thoroughness.

Nothing released by TSB on Thursday raised any issues with personal locator beacons or immersion suits.